Ignition and fuel injection back-up system for emergency running of internal combustion engines

ABSTRACT

An ignition and injection system for internal combustion engines is suggested in which a phase sensor which includes a sensor drum driven synchronously with the ignition distributor, particularly a Hall sensor drum formed with a plurality of cut-out portions, one of which is wider than the cut-out portions, and indicates the beginning of an ignition or injection cycle in emergency running. The cut-out portions produce correspondingly long timing pulses, at the beginning of which the ignition coil is charged until the trailing edge occurs and the ignition is effected. The trailing edge of the timing pulses can occur e.g. 10° before the top dead center of the respective cylinder.

BACKGROUND OF THE INVENTION

The invention is directed to an ignition and fuel injection back-upsystem for emergency running or starting internal combustion engines inwhich a Hall sensor drum is driven synchronously with a cam shaft of theengine and delivers a timing pulse to a computer at the beginning of anignition cycle, the computer controls the ignition, possibly whiletaking into account additional engine data, and the Hall sensor drum hasa cut out portion for every cylinder or every second cylinder, which cutout portions cause a corresponding quantity of timing pulses whosetrailing edges occur at a uniform rotational angle before the top deadcenter of the respective cylinder.

In ignition systems with cylinder recognition, it is known to utilizeHall sensor drums in the ignition distributor, which sensor drumcomprises a cut out portion which produces one timing pulse per 720°crankshaft revolution. During the timing pulse, a reference mark isderived e.g. from the toothed rim or from the flywheel of thecrankshaft. This reference mark occurs once per revolution of thecrankshaft, so that only every second reference mark occurs in the timeperiod of a timing signal. Accordingly, the timing signal and thereference mark together designate the beginning of an ignition cyclefrom which an exact determination of the optimal ignition times forrespective cylinders of the engine can be effected in a microprocesorwhile taking into account additional engine data, particularly whiletaking into account the speed or rate of rotation. In the event of thefailure of the transmitter for the reference mark or the speed,respectively, in such a system, the engine can no longer continue to beoperated.

SUMMARY OF THE INVENTION

In contrast, an ignition and injection system according to the inventionis characterized in that one of the cut out portions of the sensor drumis constructed so as to be wider than the others and causes a widertiming pulse relative to the rest of the timing pulses, and in that thebeginning of an ignition cycle is detected when an additional referencemark derived from a toothed rim or from the flywheel of the crankshaftoccurs during the wider timing pulse. The invention has the advantagethat the additional cut out portion in the sensor drum which areassigned to the individual top dead centers of the cylinders produce atiming signal in each instance by means of a Hall sensor, from which adefined fixed ignition angle can be determined. An enlarged cut outportion or phase window, which produces a wider timing pulse, indicatesthe beginning of an ignition cycle when a reference mark occurs in thisphase window. The other phase windows must be sufficiently narrow sothat the second reference mark does not occur therein in the course oftwo revolutions, so that an unambiguous cylinder recognition is ensured.In practice, for emergency running and possibly starting, the timingpulses represent the closing time for the ignition coil and theinjection pulses, respectively, wherein the ignition spark is producedduring the occurrence of the trailing edge of the timing pulses. Thishas the advantage not only that an emergency running ignition anglefunction is realized in a simple manner in the event of disturbance, butalso that an earlier commencement of ignition, and accordingly shorterstarting times, are achieved also when starting the engine.

The ignition angle can lie e.g. 10° before the top dead center.Moreover, the speed can be determined from the time interval between thetrailing edges, and a closing time which is adapted to the speed andduring which the ignition coil is charged can be determined by thecomputer, as can the injection time. An optimization of the emergencyrunning ignition angle function is achieved by means of this step. Theemergency running function can also be improved in that the speed isdetermined from the fixed trailing edges, a delay time for thecommencement of closing and a delay time for the ignition beingdetermined from the latter. A more accurate closing time and a morevariable ignition angle can accordingly be realized for stationaryoperation, so that overheating of the final stage can be prevented.

In normal operation which is free of disturbance, two reference marksoccur per every ignition cycle, wherein the reference mark occurring inthe middle of an ingition cycle does not coincide with a timing pulse,so that this reference mark can also not be mistakenly viewed as thestarting mark of an ignition cycle.

The measures, according to the invention, are not limited to ignitionsystems, but are also applicable to injection systems.

DRAWING

The invention is explained in more detail in the following by means ofthe drawing.

FIG. 1a shows a top view of a Hall sensor drum;

FIG. 1b shows a side view of the Hall sensor drum shown in FIG. 1a;

FIG. 2 shows a block circuit diagram of the ignition back-up system fora 4-cylinder engine;

FIG. 3 shows phase diagrams of a 4-cylinder engine, and

FIG. 4 shows phase diagrams of a 5-cylinder engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Hall sensor drum 1 shown in FIGS. 1a and 1b comprises four cut outportions 2, 3, 4, 5, the cut out portion 2 being enlarged relative tothe rest of the cut out portions 3 to 5. The Hall sensor drum 1 is builtinto the ignition distributor or on the camshaft and rotatessynchronously with the distributor rotor. A Hall sensor or probe 6,whose sensor signals are fed to an electronic engine controlling means 7(FIG. 2), is located at a slight distance from the Hall sensor drum 1.

The engine controlling means 7 in FIG. 2 produces the timing signal PSfrom the sensor signal, the timing signal PS being supplied to acomputer port 8. A signal converter 9 which converts the signal receivedfrom the Hall sensor 6 into square-wave timing pulses, is provided forpreparing the timing signal PS. Additional signal converters 10, 11 areprovided which produce square-wave reference signals BM1 and BM2 fromthe reference mark BM derived from the toothed rim of the flywheel onthe crankshaft of the engine, and a square-wave speed signal derivedfrom the speed signal n emitted by the speed sensor 12.

In the event of a failure of the reference mark BM or the speed signal ndue to a disturbance, an emergency running ignition function can berealized solely on the basis of the sensor signal sent from the Hallsensor 6.

In FIG. 3, the top dead center OT of cylinders 1 to 4 drawn in the topline is correlated to the degrees of rotation of the crankshaft KW drawnin the bottom line. Indicated below the top line is the timing signal PSwhich contains a wider timing pulse PI1 at the commencement of anignition cycle. The additional timing pulses PI2 to PI4 are shorter. Thetrailing edges R of all timing pulses PI1 to PI4 occur at 10° of thecrankshaft revolution before the top dead center OT of the respectivecylinders.

The assignment of the reference mark BM with respect to time, whichreference mark BM is already converted as square-wave reference signalBM1 or BM2, is ensured in such a way that the middle reference pulse BM2does not coincide with the timing pulses PI1 to PI4. Only the referencepulse BM1 coincides with the wider timing pulse PI1, so that thecommencement of the ignition cycle is determined in the synchronized,disturbance-free normal operation.

In the event of a failure of the reference mark signal BM due to adisturbance, an emergency running ignition function can be maintainedsolely on the basis of the timing signal PS. In this case, the ignitioncoil ZSP1 of the ignition final stage 14 (FIG. 2) is charged at thecommencement of every timing pulse of the timing signal PS and theignition is triggered in each instance at 10° before the top dead centerOT when the trailing edge R occurs. The timing signal PS accordinglydefines a fixed emergency running ignition angle which enables anemergency operation in the absence of the reference mark BM or speedsignal n.

FIG. 4 shows the corresponding diagram for a 5-cylinder engine in whicha timing pulse PI1 to PI5 is assigned to every cylinder 1 to 5. However,in this case, in the current curve of the ignition coil ZSP1 there isindicated the additional possibility that the time t_(D) between twoconsecutive trailing edges R is utilized for determining the speed. Acorrected time for the charging of the ignition coil can then becalculated from the determined speed. The case in which the closing timeT_(S) and ignition time are calculated proceeding from the precedingphase edge is also shown.

The speed can be calculated from the fixed trailing edges R, and a delaytime t_(VS) for the commencement of a closing time T_(S) during which anignition coil is charged, and a delay time t_(VZ) for the ignition timecan be determined from the latter, so that a more accurate closing timeT_(S) and a more variable ignition angle can be realized for thestationary operation.

We claim:
 1. Ignition back-up system for emergency running or startinginternal combustion engines including at least one ignition coil,comprising a computer for controlling the ignition time of the coil, asensor cooperating with a sensor drum driven synchronously with a camshaft of the engine, the sensor drum having cut out portions for everycylinder of the engine to generate by means of the sensorcylinder-related timing pulses which are delivered to the computer, thetrailing edge of the respective timing pulses occurring at a uniformrotational angle of the crankshaft of the engine before the top deadcenter of the corresponding cylinders, one of the cut out portions beingwider than the others to generate a wider timing pulse relative to therest of the timing pulses, means for generating and delivering to thecomputer a reference pulse once per revolution of the crankshaft, thereference pulse coinciding with the wider timing pulse but being spacedapart from the rest of the timing pulses, and once per revolution of thecam shaft the computer detecting the beginning of an ignition cycle whenthe reference pulse occurs during the wider timing pulse or, in theabsence of the reference pulse, during the wider timing pulse. 2.Ignition system according to claim 1, characterized in that the ignitioncoil is charged at the start of the corresponding timing pulses and theignition is triggered during their trailing edge.
 3. Ignition systemaccording to claim 1, characterized in that the trailing edge occurs ineach instance at approximately 10° before the top dead center of therespective cylinder.
 4. Ignition system according to claim 1,characterized in that the engine speed is determined from the timeinterval between the occurring trailing edges of the timing pulses, anda speed adapted time (TS) during which the ignition coil is charged asdetermined by the computer.
 5. Ignition system according to claim 1,characterized in that the trailing edges of the timing pulses areutilized for determining the ignition time only when starting the engineand/or during occurring disturbances.
 6. Ignition system according toclaim 1, characterized in that the diaphragm is utilized for producingan emergency ignition in the event of a defect in means for generatingthe reference pulse.
 7. Ignition system according to claim 1,characterized in that said sensor is a Hall sensor.
 8. Ignition systemaccording to claim 1, characterized in that the timing pulses and thereference pulses are utilized for controlling a fuel injection system ofthe engine.
 9. Ignition system according to claim 1, wherein the cut outportions of the diaphragm are assigned to every second cylinder of theengine.